add documentation to PersistEntity
add documentation to PersistEntity

mitchellwrosen/persistent,rdnetto/persistent,greydot/persistent,gbwey/persistent,greydot/persistent,nakaji-dayo/persistent,andrewthad/persistent,junjihashimoto/persistent,pseudonom/persistent,jcristovao/persistent,nakaji-dayo/persistent,andrewthad/persistent,junjihashimoto/persistent,jasonzoladz/persistent,meteficha/persistent,yesodweb/persistent,superduper/persistent,jcristovao/persistent,superduper/persistent,gbwey/persistent,naushadh/persistent,bitemyapp/persistent,greydot/persistent,mkscrg/persistent,paul-rouse/persistent,superduper/persistent,rdnetto/persistent,meteficha/persistent,nakaji-dayo/persistent,jasonzoladz/persistent,andrewthad/persistent,jcristovao/persistent,plow-technologies/persistent,mkscrg/persistent,pseudonom/persistent,jasonzoladz/persistent,mkscrg/persistent,creichert/persistent,mitchellwrosen/persistent,mitchellwrosen/persistent,gbwey/persistent,erikd/persistent,meteficha/persistent,psibi/persistent